How To: Essential Oil Solvent Extraction

What is Solvent Extraction?

The general idea with solvent extraction is that it utilizes chemical solvent. Hence, most people have a preconceived notion of this method of essential oil extraction that makes them think it produces essential oil that is not safe for use in aromatherapy. There are a few concerns with this method though since many believe it can leave residues to the resulting essential oil solution. Therefore, you need to pay close attention to the solution you are preparing and make sure to properly strain it to avoid such things from happening.

As for the process of undergoing solvent extraction, you will be adding a hydrocarbon solvent into the plant material since it aids in dissolving the essential oil. Then, the solution is filtered and undergoes a distillation process. A pure alcohol is then used to extract the essential oil from the concentrate. This method is highly recommended for plant materials that produces low yield of essential oil. It is also considered to produce oils with finer fragrance than the ones that are extracted via a distillation method.

Solvent extraction is most ideal for delicate botanical materials such as resins, flowers, and gums that is possibly destroyed by using steam, which is common in most extraction methods.

Risks With Other Extraction Methods

The plant materials used to derive essential oils are delicate and can be easily damaged with exposure to extreme conditions such as high pressure and temperature. This exposure to extreme conditions is highly probable during extraction method wherein use of heat is quite a common factor.

In an effort to preserve the natural properties of the oil, the solvent extraction method was introduced. The most focal point in this alternative method is the elimination of heat in the equation, which could ruin the natural chemicals of the essential and turn it into something toxic.

What is a Hydrocarbon Solvent?

The use of hydrocarbon solvent in this method of extraction helps in the break down of essential oil components from the plant material. As mentioned above, it does not just refer to chemical solvents. It also includes other forms of solvent contribute to dissolving the essential oil from the plant material.

Examples of chemical solvents used in this method include hexane, ether, methanol, alcohol, ethanol, and petroleum. Other types of solvents that are also commonly used to extract essential oils include fat, solid oil, and even carbon dioxide. In this process, other volatile components contained in the plant are released in the process, such as pigments and waxes. However, they are separated and only the essential oil is taken out for use.

Different Solvent Extraction Methods

Solvent extraction, like distillation method, also have different underlying methods of extraction. Each one use different types of solvent but follow a general procedure of introducing solvent materials to create three different substances: absolutes, waxes, and essential oil.

Currently, there are three known methods of solvent extraction: maceration, enfleurage, and hypercritical carbon dioxide CO2. Each one are discussed in detail below.

Maceration Method

Oils that undergo the maceration process are often referred to as macerated or infused oils. This process is mostly recommended for capturing the natural scent and fragrance of the oil. But aside from the aromatics, even the important plant constituents used for aromatherapy are recovered as well.

To undergo this procedure, you must begin by chopping up and crushing the plant materials. This action will help to open up the plant's cell walls, which hold the oil. Once the oils are released from the plant, they are “infused” and is often allowed to sit for several weeks under room temperature. Many believe that infusing fresh plants are most effective since they are able to deliver the most efficacious oils to be used in aromatherapy. A word of caution though when using fresh plant materials is that they are most likely to contain water. Hence, you must remove all water off the plant since it can cause the oil to go rancid quickly.

Enfleurage Method

The process used with the Enfleurage method is somewhat similar to the ones used with maceration, but with some slight variations too. For this one, you will be needing a chassis, which is a glass plate in frame. Coat the glass plate with animal or vegetable fat and spread the plant parts of the botanical material that you want to extract the oil from across it and press it in.

Leave the botanical materials in that greasy compound for a few days, such that the plant's essences are released into that compound. At this point, you will replace the wilted plant parts with fresh ones. Repeat the same procedure until the essences of the botanical material is fully infused into the greasy compound. You must then take an alcohol to separate the fat oil from the fragrant essences of the natural oil. By the time the alcohol evaporates from the mixture, you are left with essential oil.

Hypercritical Carbon Dioxide CO2

Among
the methods of solvent extraction, this one is relatively one of the
newest methods available. Oils produced using this method are also
considerably more expensive but with high quality oils.

For
this one, carbon dioxide is the solvent used, which reaches a
hypercritical stage at 33 degrees Celsius. At this stage, carbon
dioxide possesses the qualities of both liquid and gas. Hence, it
becomes an excellent solvent to use in extracting essential oils using
only low temperature. There is no possibility of chemical interaction
with the extracted oil since the carbon dioxide is inert. To separate
the oil from the carbon dioxide solvent, simply remove the pressure
placed in it.

Advantages of Solvent Extraction

The quality of the oil you use in aromatherapy is a huge indicator of whether the treatment is going to be a success or not. Hence, the solvent extraction method is preferred by most since it is known to produce better quality oils. To learn more about the great reasons for switching onto this method, read more below:

Instead of using heat and pressure to facilitate in the extraction of essential oils from the plant material, the use of solvents make a safer alternative. The purity of the oil is preserved since both heat and pressure are known to contribute in destroying the natural chemical composition of the plant oil.

As compared to the other extraction methods, this one is actually much friendlier to your budget. Plus, it does not take a great deal of time so you won't have to spend all day doing this.